Thurston County Washington Energy Code Compliance
WSEC-R 2021 compliance information for builders and contractors in Thurston County.
Code environment
Climate Zone
CZ4
Western Washington — west of the Cascade crest, marine climate.
Wall min R-20 cavity + R-5 continuous, or R-13 cavity + R-10 continuous · Ceiling min R-60 · Window max U-0.30 · WAC 51-11R-40213, Table R402.1.3
Radon Zone
Zone 2
Moderate radon potential — radon-resistant construction recommended but not mandated by state code.
Learn more →County building department
The county building department handles permits for unincorporated areas. Cities within the county may have their own permit offices — see below.
Authority Having Jurisdiction (AHJ)
Thurston County Development Services
- Phone
- (360) 786-5490
- Address
- 2000 Lakeridge Dr SW, Olympia, WA 98502
- Hours
- M-F 8am-5pm
Last verified: 2026-04-19
Submittal notes
- Thurston County: Thurston County: The Habitat Conservation Plan (HCP) for Mazama pocket gophers affects siting on rural parcels outside urban growth areas — verify HCP compliance before permit submittal.
Cities with their own building department
These cities have an independent permit office. If your project is inside city limits, contact the city — not the county — for permits.
Ready to check your compliance?
Answer a few questions about your project and get a complete R406 credit summary you can submit with your permit application.
Start your WSEC compliance check →Typical project costs in Thurston County
Coming soon as we gather receipt data from local contractors.
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